Gradient light beams may be utilized for capturing and/or shifting of microparticles (e.g., influencing ensembles of micro-objects in microtechnology and/or nanotechnology applications with aims including but not limited to regulating movement and/or mixing thereof with regard to organic tissues as part of therapy and/or prophylaxis and influencing materials during localized laser processing). The mechanism of particle capturing may be based on aligning particle dipoles along the direction of a light field. When the light field contains a strong gradient, the particles may be attracted to a region of strongest electric field. The gradient may influence particles in a plane perpendicular to the axis of the light field.
When the longitudinal gradient force balances a dispersion force, the particles having higher refractive index than that of the environment may be captured and localized in intensity maxima of the light field. The particles having lower refractive index than that of the environment may be retracted in local intensity minima of the light field. Optical tweezers utilized for manipulating viruses and bacteria, inducing cellular synthesis in immunology and molecular genetics, capturing and shifting chromosomes, changing mobility of human spermatozoa and trans-membrane proteins etc. may be created based on the aforementioned principle. Gradient light fields may also be utilized for creating optical pumps, funnels and the like with an aim of filtrating particles and/or influencing living and non-living matter.
Devices utilized for forming gradient light fields may not allow for locally rounded intensity maxima to be formed. Although a Fresnel biprism allows formation of a static gradient light field in the form of parallel strips, the Fresnel biprism may not allow formation of a variable gradient light field in addition to not enabling formation of a light field having locally rounded intensity maxima.
An optical setup including a source of laser radiation, a telescope-collimator and a pyramid with four edges may enable formation of a gradient light field (e.g., a quadrabeam). However, the aforementioned gradient light field may be static, with a multitude of periodically distributed intensity maxima having same magnitudes in a transverse direction.